The people best able to appreciate a rare creature's beauty are the ones whose arrival destroys it. Once they reach a remote habitat, they upset its delicate balance and drive the very species they admire toward extinction.
People are driven to possess natural beauty whatever the cost, and that drive overrides law, science and conscience. Collectors will buy from thieves and feel no remorse, so long as they get the prized object.
A passing taste for decoration can kill on an industrial scale. When exotic plumes became the mark of a stylish hat, hundreds of millions of birds were killed and whole species were pushed to the edge of extinction.
A craft can keep demanding rare materials long after any practical reason for them is gone. Ornate fishing lures are dressed with feathers from distant birds that no fish could care about, and they are rarely used to fish at all. Pure display then drives a black market in specimens.